Refrigerant compositions

ABSTRACT

A composition comprising: (i) 1,1-difluoroethene (vinylidene fluoride, R-1132a); (ii) carbon dioxide (CO 2 , R-744); (iii) pentafluoroethane (R-125); and (iv) one or more of trifluoromethane (R-23) and hexafluoroethane (R-116).

Related Applications

This application is a U.S. National Phase entry under 35 U.S.C. § 371 ofInternational Application No. PCT/GB2018/051344, filed 17 May 2018,which claims the benefit of Great Britain Patent Application No.1707909.6, filed 17 May 2017, the contents of each of which areincorporated herein by reference in their entireties.

The invention relates to compositions, preferably to heat transfercompositions, and in particular to ultra-low temperature heat transfercompositions which may be suitable as replacements for existingrefrigerants such as R-23, R-13B1, R-508A or R-508B.

The listing or discussion of a prior-published document or anybackground in the specification should not necessarily be taken as anacknowledgement that a document or background is part of the state ofthe art or is common general knowledge.

Mechanical refrigeration systems and related heat transfer devices suchas heat pumps and air-conditioning systems are well known. In suchsystems, a refrigerant liquid evaporates at low pressure taking heatfrom the surrounding zone. The resulting vapour is then compressed andpassed to a condenser where it condenses and gives off heat to a secondzone, the condensate being returned through an expansion valve to theevaporator, so completing the cycle. Mechanical energy required forcompressing the vapour and pumping the liquid is provided by, forexample, an electric motor or an internal combustion engine.

“Blast freezer” equipment is used for rapid freezing of food orpharmaceutical products by contact of the product to be frozen inside aclosed compartment with recirculating low-temperature air.

Conventional blast freezing for food uses a single stage refrigerationsystem, to generate rapid cooling down to temperatures between about −18and about −30° C. A typical refrigerant used for this would be R-404A(by weight 44% pentafluoroethane (R-125), 52% 1,1,1-trifluoroethane(R-143a) and 4% 1,1,1,2-tetrafluoroethane (R-134a)).

It has been found that using a lower cooling temperature can allow seatransport of high value seafood (e.g. sea urchin, swordfish, tuna) overlong distances. Several shipping companies offer refrigerated transportcontainer systems (‘reefers’) capable of maintaining temperatures ofabout −60° C. In these cascade systems a low temperature refrigerationloop using trifluoromethane (R-23) cools the container air to −60° C.then rejects its heat to a second higher temperature refrigeration loop(using R-134a or R-404A). The high temperature stage rejects the heat toambient air. These systems work well but the GWP of R-23 is very high at14,800. It would therefore be desirable to have a low-flammability ornon-flammable fluid of lower GWP capable of replacing R-23 in thisapplication.

The pharmaceutical industry also uses blast freezing at low temperaturesto freeze and preserve active ingredients and other biologically derivedmaterials, as discussed in the reference monograph“Freeze-Drying/Lyophilization of Pharmaceutical and Biological Products,Third Edition” edited by Louis Rey published by CRC Press, 19 Apr. 2016,incorporated by reference herein. Specific examples include, but are notlimited to, insulin, vaccines and tissue samples. Traditionalrefrigerants used in these systems include bromotrifluoromethane(R-13B1), R-23, R-508A (39% R-23, 61% R-116) and R-508B (46% R-23, 56%R-116), where the operating temperatures range from about −60° C. toabout −90° C.

There are several refrigerant and application characteristics that needto be considered in developing feasible alternatives for R-23 (and otherlow-temperature refrigerants used in cascade systems), including:

-   -   Low flammability    -   Suitable operating temperature    -   An operating pressure similar to that of R-23    -   Performance as a refrigerant (e.g. cooling capacity and energy        efficiency)    -   Minimal temperature glide of refrigerant    -   Low Global Warming Potential (GWP)

The design of a suitable refrigerant therefore involves making multipleinformed selections of composition and component to reach a feasiblealternative.

One way of assessing non-flammability is to apply the flammabilityanalysis methodology stipulated by ASHRAE Standard 34:2016, whichprescribes a range of leakage scenarios that should be applied torefrigerant blends to identify the potentially flammable worst-casecompositions.

If the fluid is to be used as a retrofit or conversion fluid in existingequipment, or as a “drop-in” to new equipment (e.g. using an essentiallyunchanged R-23 system design), then non-flammability is highly desired,as the existing design will have been based on the use of non-flammablefluid. In particular, for larger systems and marine transport (reefer)applications, non-flammability in all circumstances (including leakage)is highly preferred.

It is also advantageous to have acceptably low toxicity as acharacteristic of the fluid.

The volumetric capacity (a measure of the cooling power achievable by agiven size of compressor) and energy efficiency are importantconsiderations for any composition with heat transfer properties. Thisis especially so in cascade operation as any inefficiency in the lowtemperature stage also increases power consumption of the compressor inthe top stage of the cascade.

R-170 (ethane) has very low GWP, acceptable refrigeration performanceand low toxicity but its high flammability limits its application. Forinstance, safety regulations can restrict the maximum charge quantity ofrefrigerant in appliances.

R-744 (carbon dioxide) is non-flammable but cannot be used alone in thebottom stage of low temperature cascade systems because the operatingtemperatures are below the triple point of R-744, which is −56.7° C.This means that solid carbon dioxide (dry-ice) could form in lowpressure sections of the system, leading to blockages, poor control andinefficient operation.

R-1132a (1,1-difluoroethene, also known as vinylidene fluoride) also haslow GWP and acceptable toxicity. The flammability of R-1132a is reducedcompared to ethane but it is still in ASHRAE flammability class 2(“moderately flammable”). The thermodynamic energy efficiency of pureR-1132a is close to that of R-508 and better than that of R-23 but itsrefrigeration capacity is reduced compared to R-508 and R-23.

Thus, there is a need to provide alternative refrigerants havingimproved properties such as low GWP, yet possessing acceptablerefrigeration performance, flammability characteristics and toxicology.There is also a need to provide alternative refrigerants that may beused in existing devices such as refrigeration devices with little or nomodification.

The subject invention addresses the above and other deficiencies by theprovision of a composition comprising: 1,1-difluoroethene (vinylidenefluoride, R-1132a); carbon dioxide (CO₂, R-744); pentafluoroethane(R-125); and one or more of trifluoromethane (R-23) and hexafluoroethane(R-116).

The invention also provides the use of the compositions of the inventionas refrigerants, preferably low temperature refrigerants suitable foruse in blast freezing equipment. The temperatures reached by using thecompositions of the invention as refrigerants may be −60° C. or below,such as −70° C. or below, preferably −80° C. or below, or even −90° C.or below.

Surprisingly, it has been found that the compositions of the inventionexhibit a combination of suitable flammability properties, a similaroperating pressure to R-23, comparable or superior refrigerationperformance to R-23, desirable temperature glide and low GWP.

The compositions of the invention may comprise from about 1 to about 90%by weight R-1132a, such as from about 1 to about 80% by weight, fromabout 1 to about 70% by weight or from about 1 to about 60% by weight.Preferably, the compositions comprise from about 1 to about 50% byweight R-1132a, such as from about 5 to about 45% by weight, from about10 to about 45% by weight, from about 15 to about 40% by weight.Advantageously, the compositions may comprise from about 20 to about 40%by weight R-1132a, preferably from about 25 to about 35% by weightR-1132a.

The compositions of the invention may comprise from about 1 to about 90%by weight carbon dioxide, such as from about 1 to about 80% by weight,from about 5 to about 70% by weight or from about 10 to about 60% byweight. Preferably, the compositions comprise from about 25 to about 60%by weight carbon dioxide, such as from about 30 to about 55% by weight,or even more preferably, from about 35 to about 50% by weight.

The compositions of the invention are surprisingly able to operate below−56.7° C. (the triple point of carbon dioxide) without the formation ofdry ice in the system.

The compositions of the invention may comprise from about 1 to about 90%by weight R-125, such as from about 1 to about 80% by weight, from about1 to about 70% by weight or from about 1 to about 60% by weight.Preferably, the compositions comprise from about 1 to about 50% byweight, such as from about 5 to about 45% by weight, from about 5 toabout 30% by weight, or even from about 10 to about 25% by weight.

The compositions of the invention may comprise from about 1 to about 90%by weight of the fourth component, such as from about 1 to about 80% byweight, from about 1 to about 70% by weight or from about 1 to about 60%by weight. Preferably, the compositions of the invention can comprisefrom about 1 to about 50% by weight of the fourth component.

In an embodiment, the fourth component comprises or is R-23. Thus, apreferred composition of the invention comprises R-1132a, CO₂, R-125 andR-23.

In a preferred embodiment, there is provided a composition comprisingfrom about 20 to about 40% by weight R-1132a, from about 30 to about 60%by weight carbon dioxide, from about 1 to about 20% by weight R-23 andfrom about 1 to about 35% by weight R-125.

Advantageously, there is provided a composition comprising from about 25to about 35% by weight R-1132a, from about 35 to about 50% by weightcarbon dioxide, from about 5 to about 15% by weight R-23 and from about5 to about 30% by weight R-125.

In a preferred embodiment, there is provided a composition comprisingfrom about 25 to about 30% by weight R-1132a, from about 35 to about 50%by weight carbon dioxide, from about 10 to about 25% by weight R-125 andfrom about 5 to about 20% by weight R-23.

In an alternative embodiment, the fourth component comprises or isR-116. Thus, a preferred composition of the invention comprises R-1132a,CO₂, R-125 and R-116.

In a preferred embodiment, there is provided a composition comprisingfrom about 30 to about 60% by weight carbon dioxide, from about 10 toabout 40% by weight R-1132a, from about 5 to about 30% by weight R-125and from about 1 to about 20% by weight R-116.

A preferred composition of the invention comprises from about 35 toabout 55% by weight carbon dioxide, from about 15 to about 35% by weightR-1132a, from about 10 to about 30% by weight R-125 and from about 1 toabout 15% by weight R-116.

Advantageously, there is provided a composition comprising from about 25to about 35% by weight R-1132a (e.g. about 30%), from about 40 to about50% by weight carbon dioxide (e.g. about 45%), from about 15 to about25% by weight R-125 (e.g. about 20%) and from about 1 to about 15% byweight R-116 (e.g. about 5%).

Preferably, the R-1132a is present in an amount of less than 50% by mol.The ASHRAE fractionation analysis referred to above requires anassessment of liquid and vapour compositions during vapour leakage froma cylinder and should be conducted for two levels of refrigerant charge(15% and 90% of maximum fill) and over a range of temperatures from −40°C. to +60° C. A composition comprising less than 50% by mol. of R-1132a,preferably less than 30% by mol., will result in a weakly flammable or,preferably, a non-flammable composition under fractionation analysis.

The ASHRAE fractionation analysis is conservative in nature. The blendsof the invention, like R-23, typically will have critical temperaturesclose to ambient temperature. This means that if the system is notoperational, and warms to ambient temperature, then it is possible thatthe blend could be above its critical temperature. In this case, it willexist as a homogenous supercritical fluid. Leakage would therefore be ofthe bulk composition, not of a fractionated vapour. Therefore, if thebulk fluid is non-flammable the composition could be used for variousapplications without a significant risk of generating a flammableatmosphere.

In an embodiment, the compositions may consist essentially of the statedcomponents.

By the term “consist essentially of”, we mean that the compositions ofthe invention contain substantially no other components, particularly nofurther (hydro)(fluoro)compounds (e.g. (hydro)(fluoro)alkanes or(hydro)(fluoro)alkenes) known to be used in heat transfer compositions.The term “consist of” is included within the meaning of “consistessentially of”.

In an embodiment, the compositions of the invention are substantiallyfree of any component that has heat transfer properties (other than thecomponents specified). For instance, the compositions of the inventionmay be substantially free of any other hydrofluorocarbon compound.

By “substantially no” and “substantially free of”, we include themeaning that the compositions of the invention contain 0.5% by weight orless of the stated component, preferably 0.1% or less, based on thetotal weight of the composition.

The compositions of the invention may be azeotropic or near azeotropic,preferably azeotropic.

By azeotropic composition, we include the meaning of a composition whichat vapour-liquid equilibrium has the same composition in both phases,and whose boiling point is lower than that of the pure components. Allthe azeotropic compositions of the invention have been found to exhibita positive deviation from ideality. By near-azeotropic composition weinclude the meaning of liquid compositions whose vapour pressure isabove that of the pure component with the lower boiling point whenmeasured at equivalent temperature, but whose equilibrium vapourcomposition may differ from the liquid composition.

All of the chemicals herein described are commercially available. Forexample, the fluorochemicals may be obtained from Apollo Scientific (UK)and carbon dioxide may be obtained from liquefied gas suppliers such asLinde AG.

As used herein, all percentage amounts mentioned in compositions herein,including in the claims, are by weight based on the total weight of thecompositions, unless otherwise stated.

By the term “about”, as used in connection with numerical values ofamounts of components in % by weight, we include the meaning of ±0.5% byweight, for example ±0.2% by weight or ±0.1% by weight.

For the avoidance of doubt, it is to be understood that the stated upperand lower values for ranges of amounts of components in the compositionsof the invention described herein may be interchanged in any way,provided that the resulting ranges fall within the broadest scope of theinvention.

The compositions of the invention have zero ozone depletion potential.

The GWP is desired to be as low as possible whilst respecting the otherconstraints on flammability, performance and operational temperaturerange

The compositions have a GWP of less than 7400, such as less than 5000,less than 4000 or preferably less than 3700. The compositionsadvantageously have a GWP of less than 3000, less than 2500, less than2000, less than 1500 or even less than 1000.

Typically, the compositions of the subject invention are of reducedflammability hazard when compared to R-1132a.

Flammability may be determined in accordance with ASHRAE Standard34:2016 incorporating the ASTM Standard E-681 with test methodology asper Addendum 34p dated 2004, the entire content of which is incorporatedherein by reference.

In some embodiments, the compositions have one or more of (a) a higherlower flammable limit; (b) a higher ignition energy (sometimes referredto as auto ignition energy or pyrolysis); or (c) a lower flame velocitycompared to R-1132a alone. Preferably, the compositions of the inventionare less flammable compared to R-1132a in one or more of the followingrespects: lower flammable limit at 23° C.; lower flammable limit at 60°C.; breadth of flammable range at 23° C. or 60° C.; auto-ignitiontemperature (thermal decomposition temperature); minimum ignition energyin dry air or flame speed. The flammable limits being determinedaccording to the methods specified in ASHRAE Standard 34:2016 and theauto-ignition temperature being determined in a 500 ml glass flask bythe method of ASTM E659-78.

In a preferred embodiment, the compositions of the invention arenon-flammable. For example, the compositions of the invention arenon-flammable at a test temperature of 60° C. using the ASHRAEmethodology. Advantageously, the mixtures of vapour that exist inequilibrium with the compositions of the invention at any temperaturebetween about −40° C. and 60° C. are also non-flammable.

In some applications it may not be necessary for the formulation to beclassed as non-flammable by the ASHRAE methodology; it is possible todevelop fluids whose flammability limits will be sufficiently reduced inair to render them safe for use in the application, for example if it isphysically not possible to make a flammable mixture by leaking therefrigeration equipment charge into the surrounds.

In one embodiment, the compositions of the invention have a flammabilityclassifiable as 1 or 2 L according to the ASHRAE classification method,indicating non-flammability (class 1) or a weakly flammable fluid withflame speed lower than 10 cm/s (class 2 L).

Temperature glide can be managed within a system and glides of less thanabout 10 K are acceptable with only minor effects on performance. Glidesof greater than about 10 K can cause some degradation in expectedperformance unless heat exchangers are designed to accommodate the glideeffect.

A composition of the invention preferably have a temperature glide in anevaporator or condenser of less than about 10 K, even more preferablyless than about 7 K, such as less than about 5 K (e.g. less than 3 K).“Temperature glide” is the term given to the change in temperatureexperienced during evaporation or condensation of a non-azeotropicrefrigerant mixture.

The critical temperature of a heat transfer composition should be higherthan the maximum expected condenser temperature. This is because thecycle efficiency typically drops as critical temperature is approached.As this happens, the latent heat of the refrigerant is reduced and somore of the heat rejection in the condenser takes place by coolinggaseous refrigerant; this requires more area per unit heat transferred.The critical temperature of R-508B is about 11° C. and the criticaltemperature of R-23 is about 26° C.

In one aspect, the compositions of the invention have a criticaltemperature of greater than about 0° C., preferably greater than about10° C., more preferably greater than about 25° C.

The compositions of the invention typically have a volumetricrefrigeration capacity that is at least 85% of that of R-23 atcomparable cycle conditions. Preferably, the compositions of theinvention have a volumetric refrigeration capacity that is at least 90%of that of R-23, for example from about 95% to about 120% (e.g. about96% to about 115%) of that of R-23.

The compositions of the invention, in use as refrigerants, typically arecapable of reaching temperatures of −60° C. or lower, preferably −70° C.or lower, for example −80° C. or lower whilst maintaining theevaporation pressure above atmospheric pressure.

In one embodiment, the cycle efficiency (Coefficient of Performance,COP) of the compositions of the invention is at least 95% and/or withinabout 5% of the existing refrigerant fluid it is replacing (e.g. R-23).

Conveniently, the compressor discharge temperature of the compositionsof the invention is within about 15 K of the existing refrigerant fluidit is replacing, preferably about 10 K or even about 5 K.

The compositions of the invention are typically suitable for use inexisting designs of equipment, for example, low temperaturerefrigeration equipment and are compatible with all classes of lubricantcurrently used with established HFC refrigerants. They may be optionallystabilised or compatibilised with mineral oils by the use of appropriateadditives.

Preferably, when used in heat transfer equipment, the composition of theinvention is combined with a lubricant.

Conveniently, the lubricant is selected from the group consisting ofmineral oil, silicone oil, polyalkyl benzenes (PABs), polyol esters(POEs), polyalkylene glycols (PAGs), polyalkylene glycol esters (PAGesters), polyvinyl ethers (PVEs), poly (alpha-olefins) and combinationsthereof. PAGs and POEs (particularly the latter) are currently preferredlubricants for the compositions of the invention.

Advantageously, the lubricant further comprises a stabiliser. Thelubricant may preferably further comprise pentane (e.g. n-pentane oriso-pentane). The pentane may be present in an amount of from about 1 toabout 10% by weight, such as from about 2 to about 6% by weight of therefrigerant charge (e.g. a composition containing the pentane, lubricantand heat transfer composition).

Preferably, the stabiliser is selected from the group consisting ofdiene-based compounds, phosphates, phenol compounds and epoxides, andmixtures thereof.

Conveniently, the composition of the invention may be combined with aflame retardant.

Advantageously, the flame retardant is selected from the groupconsisting of tri-(2-chloroethyl)-phosphate, (chloropropyl) phosphate,tri-(2,3-dibromopropyl)-phosphate, tri-(1,3-dichloropropyl)-phosphate,diammonium phosphate, various halogenated aromatic compounds, antimonyoxide, aluminium trihydrate, polyvinyl chloride, a fluorinatediodocarbon, a fluorinated bromocarbon, trifluoro iodomethane,perfluoroalkyl amines, bromo-fluoroalkyl amines and mixtures thereof.

In one embodiment, the invention provides a heat transfer devicecomprising a composition of the invention.

Preferably, the heat transfer device is a refrigeration device.

Conveniently, the heat transfer device is an ultra-low temperaturerefrigeration system, such as a blast freezer.

Advantageously, the heat transfer device contains a cascade system.

The invention also provides the use of a composition of the invention ina heat transfer device as herein described.

According to a further aspect of the invention, there is provided amethod for cooling an article which comprises condensing a compositionof the invention and thereafter evaporating said composition in thevicinity of the article to be cooled.

According to another aspect of the invention, there is provided a methodfor heating an article which comprises condensing a composition of theinvention in the vicinity of the article to be heated and thereafterevaporating said composition.

According to a further aspect of the invention, there is provided amethod for extracting a substance from biomass comprising contacting thebiomass with a solvent comprising a composition of the invention, andseparating the substance from the solvent.

According to another aspect of the invention, there is provided a methodof cleaning an article comprising contacting the article with a solventcomprising a composition of the invention.

According to a further aspect of the invention, there is provided amethod for extracting a material from an aqueous solution comprisingcontacting the aqueous solution with a solvent comprising a compositionof the invention, and separating the material from the solvent.

According to another aspect of the invention, there is provided a methodfor extracting a material from a particulate solid matrix comprisingcontacting the particulate solid matrix with a solvent comprising acomposition of the invention, and separating the material from thesolvent.

According to another aspect of the invention, there is provided a methodof retrofitting a heat transfer device comprising the step of removingan existing heat transfer fluid, and introducing a composition of theinvention. Preferably, the heat transfer device is a refrigerationdevice, more preferably still the device is an ultra-low temperaturerefrigeration system, such as a blast freezer. Preferably, therefrigeration system cools a compartment to less than about −55° C.,preferably less than about −60° C., more preferably to less than about−85° C., or even less than −90° C.

Advantageously, the method further comprises the step of obtaining anallocation of greenhouse gas (e.g. carbon dioxide) emission credit.

In accordance with the retrofitting method described above, an existingheat transfer fluid can be fully removed from the heat transfer devicebefore introducing a composition of the invention. An existing heattransfer fluid can also be partially removed from a heat transferdevice, followed by introducing a composition of the invention.

The compositions of the invention may also be prepared simply by mixingthe R-1132a, carbon dioxide, R-125 and the fourth component (and furthercomponents such as a lubricant, a stabiliser or an additional flameretardant) in the desired proportions. The compositions can then beadded to a heat transfer device (or used in any other way as definedherein).

In a further aspect of the invention, there is provided a method forreducing the environmental impact arising from operation of a productcomprising an existing compound or composition, the method comprisingreplacing at least partially the existing compound or composition with acomposition of the invention. Preferably, this method comprises the stepof obtaining an allocation of greenhouse gas emission credit.

By environmental impact we include the generation and emission ofgreenhouse warming gases through operation of the product.

As mentioned above, this environmental impact can be considered asincluding not only those emissions of compounds or compositions having asignificant environmental impact from leakage or other losses, but alsoincluding the emission of carbon dioxide arising from the energyconsumed by the device over its working life. Such environmental impactmay be quantified by the measure known as Total Equivalent WarmingImpact (TEWI). This measure has been used in quantification of theenvironmental impact of certain stationary refrigeration and airconditioning equipment, including for example supermarket refrigerationsystems (see, for example,http://en.wikipedia.org/wiki/Total_equivalent_warming_impact).

The environmental impact may further be considered as including theemissions of greenhouse gases arising from the synthesis and manufactureof the compounds or compositions. In this case the manufacturingemissions are added to the energy consumption and direct loss effects toyield the measure known as Life-Cycle Carbon Production (LCCP, see forexample http://www.sae.org/events/aars/presentations/2007papasavva.pdf). The use of LCCP is common in assessing environmentalimpact of automotive air conditioning systems.

Emission credit(s) are awarded for reducing pollutant emissions thatcontribute to global warming and may, for example, be banked, traded orsold. They are conventionally expressed in the equivalent amount ofcarbon dioxide. Thus if the emission of 1 kg of R-23 is avoided then anemission credit of 1×14800=14800 kg CO₂ equivalent may be awarded.

In another embodiment of the invention, there is provided a method forgenerating greenhouse gas emission credit(s) comprising (i) replacing anexisting compound or composition with a composition of the invention,wherein the composition of the invention has a lower GWP than theexisting compound or composition; and (ii) obtaining greenhouse gasemission credit for said replacing step.

In a preferred embodiment, the use of the composition of the inventionresults in the equipment having a lower Total Equivalent Warming Impact,and/or a lower Life-Cycle Carbon Production than that which would beattained by use of the existing compound or composition.

These methods may be carried out on any suitable product, for example inthe fields of air-conditioning, refrigeration (e.g. low and mediumtemperature refrigeration), heat transfer, gaseous dielectrics, flamesuppression, solvents (e.g. carriers for flavourings and fragrances),cleaners, topical anaesthetics, and expansion applications. Preferably,the field is ultra-low temperature refrigeration.

Examples of suitable products include heat transfer devices, solventsand mechanical power generation devices. In a preferred embodiment, theproduct is a heat transfer device, such as a refrigeration device or anultra-low temperature refrigeration system.

The existing compound or composition has an environmental impact asmeasured by GWP and/or TEWI and/or LCCP that is higher than thecomposition of the invention which replaces it. The existing compound orcomposition may comprise a fluorocarbon compound, such as a perfluoro-,hydrofluoro-, chlorofluoro- or hydrochlorofluoro-carbon compound or itmay comprise a fluorinated olefin.

Preferably, the existing compound or composition is a heat transfercompound or composition such as a refrigerant. Examples of refrigerantsthat may be replaced include ULT refrigerants such as R-508A, R-508B,R-23 and R-13B1.

Any amount of the existing compound or composition may be replaced so asto reduce the environmental impact. This may depend on the environmentalimpact of the existing compound or composition being replaced and theenvironmental impact of the replacement composition of the invention.Preferably, the existing compound or composition in the product is fullyreplaced by the composition of the invention.

The invention is illustrated by the following non-limiting examples.

EXAMPLES

Compositions of R-1132a, R-744, R-125 and R-23

The performance of quaternary compositions of the invention weremodelled and the results are provided in the following Tables. Thetables list the GWP, condenser and evaporator glide, capacity and COPrelative to R-23, the difference in discharge temperature and condenserpressure, The Tables provide the contents as weight percentages, unlessotherwise specified.

The cycle conditions used in the modelling are as Table 1.

TABLE 1 Cycle conditions for modelling Reference fluid for cyclecalculation is R-23 Condensing temperature ° C. −20 Evaporatingtemperature ° C. −70 Suction gas temperature ° C. −50 Isentropicefficiency 0.65 Subcooling K 5 Evaporator superheat K 5 Cooling duty kW1 Clearance ratio 0.03 Suction line diameter for PD calculation mm 22Cycle calculation results R-23 reference Pressure ratio 7.20 Volumetricefficiency 89.3% Condenser glide K 0.0 Evaporator glide K 0.0 Evaporatorinlet temperature ° C. −70.0 Condenser exit temperature ° C. −25.0Condenser pressure bar 13.95 Evaporator pressure bar 1.94 Refrigerationeffect kJ/kg 174.1 Coefficient of Performance 1.90 Discharge temperature° C. 86.4 Mass flow rate kg/hr 20.7 Volumetric flow rate m3/hr 2.72Volumetric capacity kJ/m3 1322 Suction line pressure drop kPa/m 8.75Suction line density kg/m3 7.59 Condenser inlet density kg/m3 58.94Capacity relative to R-23 100.0% COP relative to R-23 100.0% Dischargetemperature difference K 0.0 Condenser pressure difference bar 0.00Pressure ratio relative to that of R-23 100.0%

The thermodynamic model used for the mixture calculations uses a cubicequation of state to model the vapour phase, with a Gibbs free energycorrelation (the Wilson equation) to model the liquid phase andtemperature correlations of the component vapour pressures. The binaryinteraction parameters for the fluids were correlated to measured phaseequilibrium data where available.

Many compositions have been identified that have volumetric capacitysignificantly higher than that of R-23 and may be better suited to a newsystem design to take advantage of the fluid properties.

TABLE 2 R744 60 R1132a 30 R-23 5 R125 5 Global Warming Potential (AR4basis) 916 Cycle calculation results Condenser glide K 2.5 Evaporatorglide K 2.8 Capacity relative to R-23 126.4% COP relative to R-23 97.2%Discharge temperature difference K 18.1 Condenser pressure differencebar 3.78 50 50 50 50 45 45 45 30 25 25 25 40 35 35 10 15 10 5 10 15 1010 10 15 20 5 5 10 1831 2571 2006 1441 1656 2396 1831 4.5 4.3 6.1 7.82.9 2.7 4.6 4.8 4.6 6.5 8.4 2.8 2.7 4.8 114.4% 113.1% 108.0% 103.4%119.7% 118.6% 112.7% 96.9% 95.9% 96.9% 98.1% 97.4% 96.5% 97.4% 14.1 16.714.6 12.3 9.3 11.8 10.1 2.58 2.66 1.91 1.18 2.98 3.08 2.28 45 43 43 4343 43 43 25 35 30 30 30 27 25 5 7 10 7 5 8 10 25 15 17 20 22 22 22 16161562 2076 1737 1511 1955 2251 9.4 6.4 6.9 8.0 8.6 8.5 8.4 9.7 6.8 7.28.3 9.0 8.7 8.6 96.6% 106.3% 103.5% 100.7% 99.0% 98.4% 98.0% 98.9% 98.2%97.7% 98.4% 98.9% 98.3% 97.9% 8.3 7.6 9.2 7.8 6.8 8.3 9.3 0.29 1.43 1.230.80 0.52 0.58 0.62 40 35 35 35 35 35 35 25 50 45 40 35 45 40 10 5 5 5 510 10 25 10 15 20 25 10 15 2356 1091 1266 1441 1616 1831 2006 9.3 5.06.6 8.1 9.5 4.8 6.4 9.3 5.1 6.9 8.5 9.8 4.9 6.6 93.9% 109.2% 103.3%97.9% 92.9% 108.7% 102.8% 98.5% 99.2% 99.3% 99.6% 100.0% 98.4% 98.5% 6.80.5 0.8 0.8 0.6 2.6 2.9 0.08 1.45 0.83 0.23 −0.35 1.59 0.95 60 55 55 5050 50 50 25 30 25 40 35 35 30 10 10 10 5 10 5 15 5 5 10 5 5 10 5 16561656 1831 916 1656 1091 2396 2.4 2.6 4.3 2.9 2.7 4.7 2.6 2.8 2.8 4.8 2.92.8 5.1 2.7 124.6% 123.2% 115.9% 122.8% 121.5% 115.6% 120.2% 96.1% 96.5%96.4% 98.0% 97.0% 97.8% 96.0% 21.1 17.0 18.1 10.5 13.1 11.5 15.8 3.853.59 2.86 3.20 3.30 2.48 3.39 45 45 45 45 45 45 45 35 30 30 30 30 25 255 15 10 7 5 15 10 15 10 15 18 20 15 20 1266 2571 2006 1667 1441 27462181 6.5 4.4 6.3 7.3 8.0 6.0 7.8 6.9 4.6 6.6 7.7 8.4 6.2 8.0 107.4%111.6% 106.4% 103.6% 101.8% 105.4% 100.7% 98.4% 96.5% 97.4% 98.1% 98.6%96.5% 97.6% 8.2 12.6 10.6 9.3 8.4 13.1 10.9 1.51 2.37 1.61 1.17 0.891.70 0.98 40 40 40 40 40 40 40 35 35 35 30 30 30 25 15 10 5 20 15 10 1510 15 20 10 15 20 20 2571 2006 1441 3311 2746 2181 2921 4.6 6.4 8.1 4.46.2 7.9 7.7 4.6 6.6 8.5 4.4 6.3 8.1 7.7 110.0% 104.7% 99.9% 109.1%103.9% 99.1% 98.2% 97.0% 98.0% 99.1% 96.2% 97.1% 98.2% 97.3% 8.6 6.7 4.610.9 9.0 6.9 9.2 2.05 1.29 0.57 2.13 1.39 0.67 0.76 35 35 35 35 35 35 3530 40 35 30 25 10 10 15 15 15 15 20 25 10 15 20 25 2181 2356 2571 27462921 3096 7.9 9.3 4.7 6.3 7.7 9.1 8.1 9.4 4.6 6.3 7.7 8.9 97.3% 92.3%108.2% 102.2% 96.7% 91.5% 98.8% 99.1% 97.6% 97.8% 98.0% 98.3% 3.0 2.84.7 5.0 5.1 5.0 0.34 −0.25 1.70 1.05 0.44 −0.16Compositions of R-1132a, R-744, R-125 and R-116

The performance of quaternary compositions of the invention weremodelled and the results are provided in the following Tables. Thetables list the GWP, condenser and evaporator glide, capacity and COPrelative to R-23, the difference in discharge temperature and condenserpressure, the maximum VDF in vapour and liquid, the molar percentage ofR-1132a. The Tables show the contents as weight percentages, unlessotherwise specified.

The conditions used are as set out in Table 1.

TABLE 3 R744 60 R1132a 30 R116 5 R125 5 Global Warming Potential (AR4basis) 786 Cycle calculation results Condenser glide K 2.9 Evaporatorglide K 3.3 Capacity relative to R-23 130.8% COP relative to R-23 98.7%Discharge temperature difference K 12.9 Condenser pressure differencebar 4.05 50 50 50 45 45 45 43 20 20 20 40 35 35 35 20 15 10 10 15 10 710 15 20 5 5 10 15 2791 2356 1921 1396 2006 1571 1380 5.3 7.2 8.8 3.43.5 5.4 7.1 6.9 8.7 10.0 3.8 4.0 6.2 8.0 126.1% 117.0% 108.9% 126.8%129.4% 119.3% 110.5% 99.9% 99.9% 99.9% 100.0% 100.3% 99.9% 100.0% −0.22.6 5.1 −0.2 −2.5 0.8 1.2 3.71 2.66 1.69 3.40 3.75 2.68 1.68 43 43 43 4040 40 40 25 25 25 35 35 35 30 14 12 10 15 10 5 20 18 20 22 10 15 20 102339 2165 1991 2181 1746 1311 2791 8.4 9.0 9.6 5.6 7.3 8.7 5.6 9.8 10.310.7 6.6 8.3 9.5 6.9 110.0% 106.9% 104.0% 119.0% 110.4% 102.8% 121.1%100.7% 100.8% 100.8% 100.6% 100.5% 100.5% 100.8% −2.0 −1.1 −0.2 −5.0−2.3 0.0 −7.3 1.71 1.33 0.97 2.61 1.64 0.73 2.93 35 35 35 35 35 35 35 4035 30 40 35 30 25 10 10 10 15 15 15 15 15 20 25 10 15 20 25 1746 19212096 2181 2356 2531 2706 7.3 9.0 10.6 5.7 7.5 9.2 10.9 8.2 10.0 11.6 6.58.7 10.5 12.2 107.8% 102.3% 97.4% 116.1% 109.8% 104.2% 99.1% 100.9%101.4% 102.0% 101.0% 101.3% 101.8% 102.4% −5.8 −5.9 −6.2 −8.4 −8.1 −8.3−8.6 1.24 0.63 0.04 2.19 1.52 0.89 0.28 50 50 50 50 50 50 40 35 30 30 2525 5 10 15 10 15 10 5 5 5 10 10 15 786 1396 2006 1571 2181 1746 3.2 3.33.3 5.2 5.3 7.1 3.4 3.7 4.0 6.2 6.6 8.3 126.7% 129.3% 131.9% 121.5%123.9% 114.8% 99.4% 99.7% 99.9% 99.5% 99.7% 99.6% 5.6 3.3 1.0 4.4 2.14.9 3.42 3.77 4.13 3.03 3.37 2.34 45 45 45 45 43 43 43 35 30 30 30 25 2525 5 15 10 5 20 18 16 15 10 15 20 12 14 16 1136 2181 1746 1311 2861 26872513 7.0 5.5 7.2 8.6 6.3 7.1 7.8 7.8 6.6 8.3 9.5 7.8 8.6 9.2 110.5%121.5% 112.7% 104.9% 119.8% 116.4% 113.1% 99.7% 100.2% 100.1% 100.0%100.6% 100.6% 100.7% 3.5 −1.5 1.2 3.7 −5.0 −3.9 −2.9 1.70 3.01 2.00 1.072.89 2.48 2.09 40 40 35 35 35 35 35 30 30 50 45 40 35 45 15 10 5 5 5 510 15 20 10 15 20 25 10 2356 1921 961 1136 1311 1486 1571 7.4 9.0 5.47.1 8.7 10.2 5.6 8.7 10.1 5.8 7.7 9.4 10.9 6.2 112.5% 104.8% 111.7%105.8% 100.4% 95.5% 113.9% 100.8% 100.9% 100.3% 100.5% 100.9% 101.4%100.7% −4.6 −2.3 −3.8 −3.5 −3.6 −3.9 −6.1 1.93 1.01 1.60 0.97 0.36 −0.221.89

In summary, the compositions of the invention exhibit an unexpectedcombination of advantageous properties such as (i) low- ornon-flammability, (ii) low GWP compared to existing ultra-lowtemperature refrigerants (e.g. R-23) and (iii) comparable or improvedrefrigeration performance at suitable operating temperatures andpressures compared to existing ultra-low temperature refrigerants (e.g.R-23) in terms of, for example, low glide and/or cooling capacity and/orenergy efficiency.

Preferences and options for a given aspect, feature or parameter of theinvention should, unless the context indicates otherwise, be regarded ashaving been disclosed in combination with any and all preferences andoptions for all other aspects, features and parameters of the invention.

The invention is defined by the following claims.

The invention claimed is:
 1. A composition comprising: (i)1,1-difluoroethene (vinylidene fluoride, R-1132a); (ii) carbon dioxide(CO₂, R-744); (iii) from about 10 to 25% by weight pentafluoroethane(R-125); and (iv) trifluoromethane (R-23).
 2. The composition accordingto claim 1 comprising from 1 to 90% by weight R-1132a.
 3. Thecomposition according to claim 2 comprising from 1 to 50% by weightR-1132a.
 4. The composition according to claim 1 comprising from 1 to90% by weight carbon dioxide.
 5. The composition according to claim 4comprising from 5 to 70% by weight carbon dioxide.
 6. The compositionaccording to claim 1 comprising from 1 to 90% by weight oftrifluoromethane.
 7. The composition according to claim 6 comprisingfrom 1 to 50% by weight of trifluoromethane.
 8. The compositionaccording to claim 1 comprising from 20 to 40% by weight R-1132a, from30 to 60% by weight carbon dioxide, and from 1 to 20% by weight R-23. 9.The composition according to claim 8 comprising from 25 to 35% by weightR-1132a, from 35 to 50% by weight carbon dioxide, and from 5 to 15% byweight R-23.
 10. The composition according to claim 1 comprising from 25to 30% by weight R-1132a, from 35 to 50% by weight carbon dioxide, andfrom 5 to 20% by weight R-23.
 11. The composition according to claim 1further comprising hexafluoroethane (R-116).
 12. The compositionaccording to claim 11 comprising from 30 to 60% by weight carbondioxide, from 10 to 40% by weight R-1132a, from about 10 to 25% byweight R-125, and from 1 to 20% by weight R-116.
 13. The compositionaccording to claim 1, wherein the R-1132a is present in an amount ofless than 50% by mol.
 14. The composition according to claim 13, whereinR-1132a is present in an amount of less than 30% by mol.
 15. Thecomposition according to claim 1 consisting essentially of: (i)1,1-difluoroethene (vinylidene fluoride, R-1132a); (ii) carbon dioxide(CO₂, R-744); (iii) from about 10 to 25% by weight pentafluoroethane(R-125); and (iv) trifluoromethane (R-23).
 16. The composition accordingto claim 1 which is azeotropic or near azeotropic.
 17. The compositionaccording to claim 1, wherein the composition is less flammable thanR-1132a alone.
 18. The composition according to claim 17 wherein thecomposition has a. a higher flammable limit; b. a higher ignitionenergy; and/or c. a lower flame velocity compared to R-1132a alone. 19.The composition according to claim 1 which is non-flammable.
 20. Thecomposition according to claim 1 which has a temperature glide in anevaporator or condenser of less than about 10 K.
 21. The compositionaccording to claim 20 which has a temperature glide in an evaporator ora condenser of less than 7K.
 22. The composition according to claim 1which has a critical temperature of greater than about 0° C.
 23. Thecomposition according to claim 22 which has a critical temperature ofgreater than 10° C.
 24. The composition according to claim 1 whosevolumetric refrigeration capacity is at least 90% of that of R-23 atcomparable cycle conditions.
 25. The composition according to claim 24which has a volumetric refrigeration capacity of at least 95% of that ofR-23 at comparable conditions.
 26. The composition according to claim 1whose cycle efficiency (Coefficient of Performance, COP) is at least 95%and/or within about 5% of the existing refrigerant fluid that thecomposition is replacing.
 27. The composition according to claim 1 whosecompressor discharge temperature is within 15 K of that of R-23 atcomparable cycle conditions.
 28. A composition comprising a lubricantand the composition according to claim
 1. 29. The composition accordingto claim 28, wherein the lubricant is selected from the group consistingof mineral oil, silicone oil, polyalkyl benzenes (PABs), polyol esters(POEs), polyalkylene glycols (PAGs), polyalkylene glycol esters (PAGesters), polyvinyl ethers (PVEs), poly (alpha-olefins) and combinationsthereof.
 30. The composition according to claim 29, wherein thecomposition further comprises pentane.
 31. The composition according toclaim 30, wherein the lubricant is selected from the group consisting ofPAGs and POEs.
 32. A composition comprising a stabilizer and thecomposition according to claim
 1. 33. The composition according to claim32, wherein the stabilizer is selected from the group consisting ofdiene-based compounds, phosphates, phenol compounds and epoxides, andmixtures thereof.
 34. A composition comprising a flame retardant and thecomposition according to claim
 1. 35. The composition according to claim34, wherein the flame retardant is selected from the group consisting oftri-(2-chloroethyl)-phosphate, (chloropropyl) phosphate,tri-(2,3-dibromopropyl)-phosphate, tri-(1,3-chloropropyl)-phosphate,diammonium phosphate, various halogenated aromatic compounds, antimonyoxide, aluminum trihydrate, polyvinyl chloride, a fluorinatediodocarbon, a fluorinated bromocarbon, trifluoro iodomethane,perfluoroalkyl amines, bromo-fluoroalkyl amines and mixtures thereof.36. A heat transfer device comprising the composition according toclaim
 1. 37. The heat transfer device according to claim 36 wherein theheat transfer device is a refrigeration device.
 38. The heat transferdevice according to claim 36 wherein the heat transfer device comprisesan ultra-low temperature refrigeration system.
 39. The heat transferdevice according to claim 38 wherein the heat transfer device is a blastfreezer.
 40. The heat transfer device according to claim 36 wherein theheat transfer device comprises a cascade system.
 41. A method forcooling an article which comprises condensing the composition accordingto claim 1 and thereafter evaporating the composition in the vicinity ofthe article to be cooled.
 42. A method for heating an article whichcomprises condensing the composition according to claim 1 in thevicinity of the article to be heated and thereafter evaporating thecomposition.
 43. A method for extracting a substance from biomasscomprising contacting biomass with a solvent comprising the compositionaccording to claim 1, and separating the substance from the solvent. 44.A method of cleaning an article comprising contacting the article with asolvent comprising the composition according to claim
 1. 45. A method ofextracting a material from an aqueous solution or from a particulatesolid matrix comprising contacting the aqueous solution or theparticulate solid matrix with a solvent comprising the compositionaccording to claim 1, and separating the material from the solvent. 46.A method of retrofitting a heat transfer device comprising removing anexisting heat transfer composition, and introducing the compositionaccording to claim
 1. 47. The method according to claim 46 wherein theheat transfer composition is a refrigerant selected from the groupconsisting of R-508A, R-508B, R-23 and R-13B1.
 48. The method accordingto claim 46 wherein the heat transfer device is a refrigeration device.49. The method according to claim 48 wherein the refrigeration devicecools a compartment to less than about −60° C.
 50. The method accordingto claim 49 wherein the refrigeration device cools a compartment to lessthan −70° C.
 51. A method for reducing an environmental impact arisingfrom an operation of a product comprising an existing compound orcomposition, the method comprising replacing at least partially theexisting compound or composition with the composition according toclaim
 1. 52. The method according to claim 51 carried out on a productfrom the fields of air-conditioning, refrigeration, heat transfer,gaseous dielectrics, flame suppression, solvents, cleaners, topicalanesthetics, and expansion applications.
 53. The method according toclaim 51 wherein the product is selected from the group consisting of aheat transfer device and a solvent.
 54. The method according to claim 53wherein the product is a heat transfer device.
 55. The method accordingto claim 54 wherein the product is an ultra-low temperaturerefrigeration system.
 56. The method according to claim 53 wherein theproduct is a heat transfer device.
 57. The method according to claim 51wherein the existing compound or composition is a heat transfercomposition.
 58. The method according to claim 55 wherein the heattransfer composition is a refrigerant selected from the group consistingof R-508A, R-508B, R-23 and R-13B1.
 59. A method for generatinggreenhouse gas emission credit comprising (i) replacing an existingcompound or composition with the composition according to claim 1,wherein the composition according to claim 1 has a lower GWP than theexisting compound or composition; and (ii) obtaining greenhouse gasemission credit for said replacing.
 60. The method according to claim 59wherein the use of the composition according to claim 1 results in alower Total Equivalent Warming Impact, and/or a lower Life-Cycle CarbonProduction than is attained by use of the existing compound orcomposition.